We studied five patients (two men and three women, age between 58 and 76 years) with clinical and electrophysiological signs of polyneuropathy. Routine neurological, hematological, and gastroenterological studies as well as procedures to test fat malabsorption were performed. Folate determinations were done using both radioactive and Lactobacillus casei methods. Two patients displayed the signs of subacute combined degeneration of the spinal cord with polyneuropathy, while three had only signs of neuropathy. All had low serum folate concentration, long-standing gastrointestinal disease, and deficient folate intake. The D-xylose absorption test gave values in all patients, while none displayed the classical malabsorption syndrome. The patients had substantial improvement or recovered (according to clinical and electrophysiological measurements) after periods ranging from 9 to 39 months of folate therapy. Such acquired folate-responsive polyneuropathy has two principal characteristics: mixed sensorimotor with mainly sensory deficits, and involvement of one or both of the lower extremities much more extensively than the upper extremities.